Abstract: Objective　To investigate the effect of different incremental work rates on the peak respiratory exchange ratio（RER） during symptom-limited maximal cardiopulmonary exercise testing（CPET） in healthy individuals，in order to provide a reference for the determination of peak RER as an indicator of achieving a maximal effort and stopping exercise.Methods　Six healthy volunteers who studied and worked at Fuwai Hospital，Chinese Academy of Medical Sciences，were recruited from October to December 2016.After signing the written informed consent，in the Cardiopulmonary Exercise Testing Room，they underwent the symptom-limited maximal CPET at the same period of time in two working days with different incremental work rates（the CPET was performed with an incremental work rate of 10 W/min on the first day，and with an incremental work rate of 30-60 W/min on the second day based on age，sex and predicted values of the CPET）．The mean values of the key parameters（exercise duration，RER，V?O2，WR，HR，O2P，AT，V?E/V?CO2-lowest 90 s，OUEP） and RER at different phases of CPETs with low and high incremental work rates were calculated and analyzed comparatively.Results　The mean exercise duration was longer〔（1 133±150）s vs （491±81）s，P<0.001）〕，mean peak RER was lower〔（1.13±0.08）vs （1.31±0.14），P=0.004〕，mean peak WR was lower〔（157±25） W/min vs （212±48）W/min，P=0.010〕 for symptom-limited maximal CPET performed with an incremental work rate of 10 W/min compared with those of the CPET performed with an incremental work rate of 30-60 W/min.The CPETs performed with incremental work rates of 10 W/min and 30-60 W/min showed no significant differences in the mean values of RER at rest，warm-up and AT（P>0.05），except that the mean RER at peak phase was lower for the former （P<0.05）．Conclusion　The value of peak RER of CPET among the healthy individuals changes significantly according to the incremental work rate.In clinical practice，we should neither simply stop the exercising of the patient when the peak RER reaching a specific level nor deny the maximal effort of the symptom-limited CPET has been achieved if the peak RER does not reach a specific level.

Key words: Respiratory function tests, Respiratory exchange ratio, Work rate-increasing rate, Cardiopulmonary exercise testing, Standard for stopping exercise, Safety and risk

摘要： 目的　观察正常人在不同功率递增速率下完成症状限制性极限运动心肺运动试验（CPET）对峰值呼吸交换率（RER）的影响，以探讨峰值RER能否作为判定受试者达到最大极限运动状态的依据和停止运动的指征。方法　2016年10—12月选取6例在中国医学科学院阜外医院学习工作、无任何疾病的健康志愿者为研究对象，签署知情同意书后于中国医学科学院阜外医院CPET实验室完成症状限制性最大极限CPET。先后在两个不同工作日的同一时间段，分别在第1天直接用10 W/min完成低功率递增速率CPET；次日根据健康志愿者的年龄、性别和其预计值等，以30~60 W/min完成高功率递增速率CPET。分别计算并比较两次CPET的核心指标〔运动时间，峰值运动时的呼吸交换率（RER）、摄氧量（O2）、功率负荷（WR）、心率（HR）和脉搏（O2P）、无氧阈（AT）、二氧化碳通气有效性平均90s最低值（V?E/V?CO2-lowest 90s）和摄氧有效性峰值平台（OUEP）〕和CPET各时段的RER。结果　低功率递增速率CPET运动时间长于高功率递增速率CPET〔（1 133±150）s 与 （491±81）s，P<0.001）〕，峰值RER、峰值WR低于高功率递增速率CPET〔（1.13±0.08）与（1.31±0.14），P=0.004；（157±25） W/min 与 （212±48）W/min，P=0.010〕。两次CPET在静息期、热身期和AT时RER比较，差异无统计学意义（P>0.05）；低功率递增速率CPET峰值时RER低于高功率递增速率CPET（P<0.05）。结论　正常人选择不同的功率递增速率能显著地改变CPET的峰值RER。CPET临床实施中，既不能机械地以达到某个特定RER值作为停止运动的标准，也不能以峰值RER未达到某个特定值来否定受试者的症状限制性极限运动的CPET为极限运动。

关键词: 呼吸功能试验, 呼吸交换率, 功率递增速率, 心肺运动试验, 终止运动标准, 安全与风险